The recording material employing color development through a reaction between a color former and a color-developing agent, since record may be made by a relatively simple apparatus in a short time without applying a complicated treatment such as development and fixation, are widely used in e.g., thermal recording paper for output-recording from a facsimile, a printer or the like, or pressure-sensitive copying paper of a ledger sheet for simultaneous copying to several sheets.
Among the compounds serving as a color-developing agent, some compounds are known to have different crystal forms (see, Patent Documents 1, 2, 3). The present inventors have already proposed a recording material using a non-phenol compound such as N-(2-(3-phenylureido)phenyl)benzenesulfonamide as a color-developing agent and having excellent e.g., background heat-resistance (see Patent Document 4). Such non-phenol compounds are known not only as a color-developing agent but also a useful compound in medicinal use (see, Patent Document 5). Whether a compound having different crystal forms is present in these compounds has not yet been known. However, a compound may have different properties in using as a recording material depending upon the difference in crystal form. If such a crystal form is present, it will be extremely useful.